1. Field of the Invention
The present invention relates to a method for manufacturing an electronic part comprising a substrate on which an electronic circuit, such as an electronic tuner or a voltage control oscillator, is provided and a shield case covering the substrate. The present invention further relates to electronic parts using this method.
2. Description of the Related Art
Nowadays, as electronic apparatuses become smaller with their performance more improved, the substrate of an electronic part on which an electronic circuit is provided is covered with a shield case consisting of a plate material of pure iron, Permalloy or the like in order to prevent interference from or to another circuit.
A conventional method for manufacturing an electronic part equipped with a shield case will be described with reference to the drawings.
In FIG. 6, numeral 21 indicates a mother board which is to be separated into a plurality of substrates by being cut. The mother board 21 is formed by stacking together a plurality of ceramic sheets (not shown) on which electronic circuits are printed. By cutting the mother board 21 along border lines 22a and 22b, a number of substrates 23 constituting electronic parts 30 described later can be obtained.
In this mother board 21, through-holes 24 having a substantially oval opening are provided such that they extend along the border lines 22a and 22b
The mother board 21 is cut along the border lines 22a and 22b into a plurality of substrates 23. In this process, the through-holes 24 are divided, with the result that a recess 25 is formed on each side of each substrate 23, as shown in FIG. 7.
Next, as shown in FIG. 8, solder 26 is applied to each recess 25 by a soldering iron (not shown), and then a shield case 27 is attached to the substrate 23. The shield case 27 is formed of metal and is equipped with a plurality of legs 27a, which are fitted into the recesses 25 of the substrate 23.
Next, the solder 26 undergoes a reflow soldering process, whereby the legs 27a of the shield case 27 is secured to the recesses 25 of the substrate 23.
In this way, as shown in FIG. 9, an electronic part 30 wherein a shield case 27 is mounted to a substrate is obtained.
In this conventional method for manufacturing electronic parts, since solder is applied to the recesses formed in each substrate, after separating the mother board, the soldering operation is troublesome.
Further, the application of solder, which is effected manually or by using a mechanic nozzle, is rather difficult to perform since the section where the solder is applied (recess) is small. As a result, in electronic parts obtained by such a manufacturing method, some solder is allowed to lie off the sides of the substrate, thereby generating so-called solder "bumps" or solder "horns", resulting in a deterioration in the dimensional accuracy of the electronic part, namely causing variation in outward dimensions.
Further still, the operation of attaching a shield case to each of the substrates obtained through separation is troublesome.
Moreover, each electronic part must be checked to make sure whether the attachment of the shield case by soldering has been properly performed, and this checking operation is troublesome.